I never played online games but id like to start what do i do
Do you intend to run a game or play in one? If you want to run one you start a thread like you did and list what your campaign is and what system and what your requirements for player characters are. Then you wait for submissions. Sometimes you get a lot and will need to be choosy.
If you want to play you look for a recruitment post and follow the instructions given to make a character.
Start there and then go through some of the other stickied guides in the PbP discussion forum. Then try applying for a game and seeing if you like it. Recruitment can be hard given that there are many more players than DMs, so expect to apply 3-5 times before getting picked, and try to keep polishing your submissions so that they have a better chance.